FIG. 1 illustrates a conventional Schottky diode 10. As seen from this structure, the forward current for the Schottky diode 10 flows from the anode 12 into the N-well 11/N-epi 13/NBL 14 and is collected by N-sinker diffusion 16. The N-sinker diffusion 16 in conjunction with N-type buried layer (NBL) 14 is used to reduce the series cathode resistance of the Schottky diode 10.
Conventional Schottky diodes conduct in forward mode when the anode to cathode voltage exceeds the metal to semiconductor barrier potential. However, for some applications, for example, voltage converter applications, a forward blocking Schottky diode is desirable to disconnect the input voltage appearing at its anode with the cathode that drives the load.
One solution that is used in the industry is to use synchronous rectification. In synchronous rectification the body diode of NMOS+the channel current—however then you cannot impede current through the body diode. But if the body of the NMOS is switched then it is possible to impede the current; however, if the body is switched, i.e., the body is tied to source/inductor and drain/cathode to load during forward conduction and the body gets switched to ground when no current is desired, this requires a low resistance switch to short the body to source and the switch must be able to carry current so the circuitry gets complicated. Accordingly, synchronous rectification requires additional level shifting and driving circuitry for the NMOSFET that impacts the efficiency of the part at higher voltages. Due to the above mentioned reasons, a Schottky diode that is capable of both forward and reverse blocking is desirable.
The present invention addresses such a need.